1. Field of the Invention
This invention relates to camera systems having distance measuring apparatus and more particularly to a camera system having a distance measuring apparatus for automatically focusing.
2. Related Art Statement
Recently, most of the operations in a camera which have been conventionally operated by hand are being automated and accordingly the focusing technique of the camera, that is, the technique of automatically focusing an object hard to focus has been improved. However, the technique of automatically focusing the below described objects, that is,
(1) an object present outside the center of a photographed picture and
(2) a moving object is particularly difficult and has been desired to be improved.
As conventional technical means for automatically focusing these objects and preventing defocusing, corresponding to the above mentioned respective items (1) and (2), there have been two techniques including:
[1] a multi-point distance measuring technique of measuring distances to objects present at a plurality of points within a photographed picture and
[2] a moving object distance measuring technique wherein a distance to an object present at a point within a photographed picture is measured, then the distance to the object present at this point is measured by delaying the time, these measurements are made a plurality of times, on the basis of the results of these distance measurements, the moving speed of the object is detected and thereby the focus lag with the movement of the object as produced during the release time lag is prevented. Regarding the latter moving object distance measuring technique, for example, a detecting apparatus for detecting the speed of a moving object on a belt conveyer is disclosed in the publication of Japanese patent application laid open No.23257/1987 and an automatic focus adjusting apparatus whereby an automatically focused state can be maintained irrespective of the motion of the object is disclosed in the publication of Japanese patent application laid open No.159817/1988.
However, in the above mentioned two techniques, that is, the multi-point distance measuring technique and moving object distance measuring technique, there is a problem that time is taken to measure the distance to the object. That is to say, on the above mentioned paragraph [1], the more the number of points for measuring the distances to the objects, the longer the time required to measure the distances. On the above mentioned paragraph [2], the distance measurement while delaying the time is required a plurality of times and the time required to measure the distance will be long. Therefore, in both of the distance measuring techniques in the above mentioned paragraphs [1] and [2], the release time lag has been likely to be produced.
That is to say, in the camera having the multi-point distance measuring function and moving object distance measuring function, with merely combining these techniques, the release time lag will become long and the precious shutter chance is likely to be missed.